Programmable Power Management Agent

ABSTRACT

In an embodiment, a processor includes a first core and a power management agent (PMA), coupled to the first core, to include a static table that stores a list of operations, and a plurality of columns each to specify a corresponding flow that includes a corresponding subset of the operations. Execution of each flow is associated with a corresponding state of the first core. The PMA includes a control register (CR) that includes a plurality of storage elements to receive one of a first value and a second value. The processor includes execution logic, responsive to a command to place the first core into a first state, to execute an operation of a first flow when a corresponding storage element stores the first value and to refrain from execution of an operation of the first flow when the corresponding element stores the second value. Other embodiments are described and claimed.

This application is a divisional of U.S. patent application Ser. No.14/634,777, filed Feb. 28, 2015, the content of which is herebyincorporated by reference.

TECHNICAL FIELD

Embodiments relate to power management of a system, and moreparticularly to power management of a multicore processor.

BACKGROUND

Advances in semiconductor processing and logic design have permitted anincrease in the amount of logic that may be present on integratedcircuit devices. As a result, computer system configurations haveevolved from a single or multiple integrated circuits in a system tomultiple hardware threads, multiple cores, multiple devices, and/orcomplete systems on individual integrated circuits. Additionally, as thedensity of integrated circuits has grown, the power requirements forcomputing systems (from embedded systems to servers) have alsoescalated. Furthermore, software inefficiencies, and its requirements ofhardware, have also caused an increase in computing device energyconsumption. In fact, some studies indicate that computing devicesconsume a sizeable percentage of the entire electricity supply for acountry, such as the United States of America. As a result, there is avital need for energy efficiency and conservation associated withintegrated circuits. These needs will increase as servers, desktopcomputers, notebooks, Ultrabooks™, tablets, mobile phones, processors,embedded systems, etc. become even more prevalent (from inclusion in thetypical computer, automobiles, and televisions to biotechnology).

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of a portion of a system in accordance with anembodiment of the present invention.

FIG. 2 is a block diagram of a processor in accordance with anembodiment of the present invention.

FIG. 3 is a block diagram of a multi-domain processor in accordance withanother embodiment of the present invention.

FIG. 4 is an embodiment of a processor including multiple cores.

FIG. 5 is a block diagram of a micro-architecture of a processor core inaccordance with one embodiment of the present invention.

FIG. 6 is a block diagram of a micro-architecture of a processor core inaccordance with another embodiment.

FIG. 7 is a block diagram of a micro-architecture of a processor core inaccordance with yet another embodiment.

FIG. 8 is a block diagram of a micro-architecture of a processor core inaccordance with a still further embodiment.

FIG. 9 is a block diagram of a processor in accordance with anotherembodiment of the present invention.

FIG. 10 is a block diagram of a representative SoC in accordance with anembodiment of the present invention.

FIG. 11 is a block diagram of another example SoC in accordance with anembodiment of the present invention.

FIG. 12 is a block diagram of an example system with which embodimentscan be used.

FIG. 13 is a block diagram of another example system with whichembodiments may be used.

FIG. 14 is a block diagram of a representative computer system.

FIG. 15 is a block diagram of a system in accordance with an embodimentof the present invention.

FIG. 16 is a block diagram of a system, according to an embodiment ofthe present invention.

FIG. 17 is a block diagram of a portion of a power management agent(PMA), according to an embodiment of the present invention.

FIG. 18 is a flow diagram of a method, according to an embodiment of thepresent invention.

FIG. 19 is a flow diagram of a method, according to another embodimentof the present invention.

FIG. 20 is a flow diagram of a method, according to another embodimentof the present invention.

DETAILED DESCRIPTION

Although the following embodiments are described with reference toenergy conservation and energy efficiency in specific integratedcircuits, such as in computing platforms or processors, otherembodiments are applicable to other types of integrated circuits andlogic devices. Similar techniques and teachings of embodiments describedherein may be applied to other types of circuits or semiconductordevices that may also benefit from better energy efficiency and energyconservation. For example, the disclosed embodiments are not limited toany particular type of computer systems. That is, disclosed embodimentscan be used in many different system types, ranging from servercomputers (e.g., tower, rack, blade, micro-server and so forth),communications systems, storage systems, desktop computers of anyconfiguration, laptop, notebook, and tablet computers (including 2:1tablets, phablets and so forth), and may be also used in other devices,such as handheld devices, systems on chip (SoCs), and embeddedapplications. Some examples of handheld devices include cellular phonessuch as smartphones, Internet protocol devices, digital cameras,personal digital assistants (PDAs), and handheld PCs. Embeddedapplications may typically include a microcontroller, a digital signalprocessor (DSP), network computers (NetPC), set-top boxes, network hubs,wide area network (WAN) switches, wearable devices, or any other systemthat can perform the functions and operations taught below. More so,embodiments may be implemented in mobile terminals having standard voicefunctionality such as mobile phones, smartphones and phablets, and/or innon-mobile terminals without a standard wireless voice functioncommunication capability, such as many wearables, tablets, notebooks,desktops, micro-servers, servers and so forth. Moreover, theapparatuses, methods, and systems described herein are not limited tophysical computing devices, but may also relate to softwareoptimizations for energy conservation and efficiency. As will becomereadily apparent in the description below, the embodiments of methods,apparatuses, and systems described herein (whether in reference tohardware, firmware, software, or a combination thereof) are vital to a‘green technology’ future, such as for power conservation and energyefficiency in products that encompass a large portion of the US economy.

Referring now to FIG. 1, shown is a block diagram of a portion of asystem in accordance with an embodiment of the present invention. Asshown in FIG. 1, system 100 may include various components, including aprocessor 110 which as shown is a multicore processor. Processor 110 maybe coupled to a power supply 150 via an external voltage regulator 160,which may perform a first voltage conversion to provide a primaryregulated voltage to processor 110.

As seen, processor 110 may be a single die processor including multiplecores 120 _(a)-120 _(n). In addition, each core may be associated withan integrated voltage regulator (IVR) 125 _(a)-125 _(n) which receivesthe primary regulated voltage and generates an operating voltage to beprovided to one or more agents of the processor associated with the IVR.Accordingly, an IVR implementation may be provided to allow forfine-grained control of voltage and thus power and performance of eachindividual core. As such, each core can operate at an independentvoltage and frequency, enabling great flexibility and affording wideopportunities for balancing power consumption with performance. In someembodiments, the use of multiple IVRs enables the grouping of componentsinto separate power planes, such that power is regulated and supplied bythe IVR to only those components in the group. During power management,a given power plane of one IVR may be powered down or off when theprocessor is placed into a certain low power state, while another powerplane of another IVR remains active, or fully powered.

Still referring to FIG. 1, additional components may be present withinthe processor including an input/output interface 132, another interface134, and an integrated memory controller 136. As seen, each of thesecomponents may be powered by another integrated voltage regulator 125_(x). In one embodiment, interface 132 may be enable operation for anIntel® Quick Path Interconnect (QPI) interconnect, which provides forpoint-to-point (PtP) links in a cache coherent protocol that includesmultiple layers including a physical layer, a link layer and a protocollayer. In turn, interface 134 may communicate via a Peripheral ComponentInterconnect Express (PCIe™) protocol.

Also shown is a power control unit (PCU) 138, which may includehardware, software and/or firmware to perform power managementoperations with regard to processor 110. As seen, PCU 138 providescontrol information to external voltage regulator 160 via a digitalinterface to cause the voltage regulator to generate the appropriateregulated voltage. PCU 138 also provides control information to IVRs 125via another digital interface to control the operating voltage generated(or to cause a corresponding IVR to be disabled in a low power mode). Invarious embodiments, PCU 138 may include a variety of power managementlogic units to perform hardware-based power management. Such powermanagement may be wholly processor controlled (e.g., by variousprocessor hardware, and which may be triggered by workload and/or power,thermal or other processor constraints) and/or the power management maybe performed responsive to external sources (such as a platform ormanagement power management source or system software).

While not shown for ease of illustration, understand that additionalcomponents may be present within processor 110 such as uncore logic, andother components such as internal memories, e.g., one or more levels ofa cache memory hierarchy and so forth. Furthermore, while shown in theimplementation of FIG. 1 with an integrated voltage regulator,embodiments are not so limited.

Note that the power management techniques described herein may beindependent of and complementary to an operating system (OS)-based powermanagement (OSPM) mechanism. According to one example OSPM technique, aprocessor can operate at various performance states or levels, so-calledP-states, namely from P0 to PN. In general, the P1 performance state maycorrespond to the highest guaranteed performance state that can berequested by an OS. In addition to this P1 state, the OS can furtherrequest a higher performance state, namely a P0 state. This P0 state maythus be an opportunistic or turbo mode state in which, when power and/orthermal budget is available, processor hardware can configure theprocessor or at least portions thereof to operate at a higher thanguaranteed frequency. In many implementations a processor can includemultiple so-called bin frequencies above the P1 guaranteed maximumfrequency, exceeding to a maximum peak frequency of the particularprocessor, as fused or otherwise written into the processor duringmanufacture. In addition, according to one OSPM mechanism, a processorcan operate at various power states or levels. With regard to powerstates, an OSPM mechanism may specify different power consumptionstates, generally referred to as C-states, C0, C1 to Cn states. When acore is active, it runs at a C0 state, and when the core is idle it maybe placed in a core low power state, also called a core non-zero C-state(e.g., C1-C6 states), with each C-state being at a lower powerconsumption level (such that C6 is a deeper low power state than C1, andso forth).

Understand that many different types of power management techniques maybe used individually or in combination in different embodiments. Asrepresentative examples, a power controller may control the processor tobe power managed by some form of dynamic voltage frequency scaling(DVFS) in which an operating voltage and/or operating frequency of oneor more cores or other processor logic may be dynamically controlled toreduce power consumption in certain situations. In an example, DVFS maybe performed using Enhanced Intel SpeedStep™ technology available fromIntel Corporation, Santa Clara, Calif., to provide optimal performanceat a lowest power consumption level. In another example, DVFS may beperformed using Intel TurboBoost™ technology to enable one or more coresor other compute engines to operate at a higher than guaranteedoperating frequency based on conditions (e.g., workload andavailability).

Another power management technique that may be used in certain examplesis dynamic swapping of workloads between different compute engines. Forexample, the processor may include asymmetric cores or other processingengines that operate at different power consumption levels, such that ina power constrained situation, one or more workloads can be dynamicallyswitched to execute on a lower power core or other compute engine.Another exemplary power management technique is hardware duty cycling(HDC), which may cause cores and/or other compute engines to beperiodically enabled and disabled according to a duty cycle, such thatone or more cores may be made inactive during an inactive period of theduty cycle and made active during an active period of the duty cycle.Although described with these particular examples, understand that manyother power management techniques may be used in particular embodiments.

Embodiments can be implemented in processors for various marketsincluding server processors, desktop processors, mobile processors andso forth. Referring now to FIG. 2, shown is a block diagram of aprocessor in accordance with an embodiment of the present invention. Asshown in FIG. 2, processor 200 may be a multicore processor including aplurality of cores 210 _(a)-210 _(n). In one embodiment, each such coremay be of an independent power domain and can be configured to enter andexit active states and/or maximum performance states based on workload.The various cores may be coupled via an interconnect 215 to a systemagent or uncore 220 that includes various components. As seen, theuncore 220 may include a shared cache 230 which may be a last levelcache. In addition, the uncore may include an integrated memorycontroller 240 to communicate with a system memory (not shown in FIG.2), e.g., via a memory bus. Uncore 220 also includes various interfaces250 and a power control unit 255, which may include logic to perform thepower management techniques described herein.

In addition, by interfaces 250 a-250 n, connection can be made tovarious off-chip components such as peripheral devices, mass storage andso forth. While shown with this particular implementation in theembodiment of FIG. 2, the scope of the present invention is not limitedin this regard.

Referring now to FIG. 3, shown is a block diagram of a multi-domainprocessor in accordance with another embodiment of the presentinvention. As shown in the embodiment of FIG. 3, processor 300 includesmultiple domains. Specifically, a core domain 310 can include aplurality of cores 310 ₀-310 _(n), a graphics domain 320 can include oneor more graphics engines, and a system agent domain 350 may further bepresent. In some embodiments, system agent domain 350 may execute at anindependent frequency than the core domain and may remain powered on atall times to handle power control events and power management such thatdomains 310 and 320 can be controlled to dynamically enter into and exithigh power and low power states. Each of domains 310 and 320 may operateat different voltage and/or power. Note that while only shown with threedomains, understand the scope of the present invention is not limited inthis regard and additional domains can be present in other embodiments.For example, multiple core domains may be present each including atleast one core.

In general, each core 310 may further include low level caches inaddition to various execution units and additional processing elements.In turn, the various cores may be coupled to each other and to a sharedcache memory formed of a plurality of units of a last level cache (LLC)340 ₀-340 _(n). In various embodiments, LLC 340 may be shared amongstthe cores and the graphics engine, as well as various media processingcircuitry. As seen, a ring interconnect 330 thus couples the corestogether, and provides interconnection between the cores, graphicsdomain 320 and system agent circuitry 350. In one embodiment,interconnect 330 can be part of the core domain. However in otherembodiments the ring interconnect can be of its own domain.

As further seen, system agent domain 350 may include display controller352 which may provide control of and an interface to an associateddisplay. As further seen, system agent domain 350 may include a powercontrol unit 355 which can include logic to perform the power managementtechniques described herein.

As further seen in FIG. 3, processor 300 can further include anintegrated memory controller (IMC) 370 that can provide for an interfaceto a system memory, such as a dynamic random access memory (DRAM).Multiple interfaces 380 ₀-380 _(n). may be present to enableinterconnection between the processor and other circuitry. For example,in one embodiment at least one direct media interface (DMI) interfacemay be provided as well as one or more PCIe™ interfaces. Still further,to provide for communications between other agents such as additionalprocessors or other circuitry, one or more QPI interfaces may also beprovided. Although shown at this high level in the embodiment of FIG. 3,understand the scope of the present invention is not limited in thisregard.

Referring to FIG. 4, an embodiment of a processor including multiplecores is illustrated. Processor 400 includes any processor or processingdevice, such as a microprocessor, an embedded processor, a digitalsignal processor (DSP), a network processor, a handheld processor, anapplication processor, a co-processor, a system on a chip (SoC), orother device to execute code. Processor 400, in one embodiment, includesat least two core—cores 401 and 402, which may include asymmetric coresor symmetric cores (the illustrated embodiment). However, processor 400may include any number of processing elements that may be symmetric orasymmetric.

In one embodiment, a processing element refers to hardware or logic tosupport a software thread. Examples of hardware processing elementsinclude: a thread unit, a thread slot, a thread, a process unit, acontext, a context unit, a logical processor, a hardware thread, a core,and/or any other element, which is capable of holding a state for aprocessor, such as an execution state or architectural state. In otherwords, a processing element, in one embodiment, refers to any hardwarecapable of being independently associated with code, such as a softwarethread, operating system, application, or other code. A physicalprocessor typically refers to an integrated circuit, which potentiallyincludes any number of other processing elements, such as cores orhardware threads.

A core often refers to logic located on an integrated circuit capable ofmaintaining an independent architectural state, wherein eachindependently maintained architectural state is associated with at leastsome dedicated execution resources. In contrast to cores, a hardwarethread typically refers to any logic located on an integrated circuitcapable of maintaining an independent architectural state, wherein theindependently maintained architectural states share access to executionresources. As can be seen, when certain resources are shared and othersare dedicated to an architectural state, the line between thenomenclature of a hardware thread and core overlaps. Yet often, a coreand a hardware thread are viewed by an operating system as individuallogical processors, where the operating system is able to individuallyschedule operations on each logical processor.

Physical processor 400, as illustrated in FIG. 4, includes two cores,cores 401 and 402. Here, cores 401 and 402 are considered symmetriccores, i.e., cores with the same configurations, functional units,and/or logic. In another embodiment, core 401 includes an out-of-orderprocessor core, while core 402 includes an in-order processor core.However, cores 401 and 402 may be individually selected from any type ofcore, such as a native core, a software managed core, a core adapted toexecute a native instruction set architecture (ISA), a core adapted toexecute a translated ISA, a co-designed core, or other known core. Yetto further the discussion, the functional units illustrated in core 401are described in further detail below, as the units in core 402 operatein a similar manner.

As depicted, core 401 includes two hardware threads 401 a and 401 b,which may also be referred to as hardware thread slots 401 a and 401 b.Therefore, software entities, such as an operating system, in oneembodiment potentially view processor 400 as four separate processors,i.e., four logical processors or processing elements capable ofexecuting four software threads concurrently. As alluded to above, afirst thread is associated with architecture state registers 401 a, asecond thread is associated with architecture state registers 401 b, athird thread may be associated with architecture state registers 402 a,and a fourth thread may be associated with architecture state registers402 b. Here, each of the architecture state registers (401 a, 401 b, 402a, and 402 b) may be referred to as processing elements, thread slots,or thread units, as described above. As illustrated, architecture stateregisters 401 a are replicated in architecture state registers 401 b, soindividual architecture states/contexts are capable of being stored forlogical processor 401 a and logical processor 401 b. In core 401, othersmaller resources, such as instruction pointers and renaming logic inallocator and renamer block 430 may also be replicated for threads 401 aand 401 b. Some resources, such as re-order buffers inreorder/retirement unit 435, ILTB 420, load/store buffers, and queuesmay be shared through partitioning. Other resources, such as generalpurpose internal registers, page-table base register(s), low-leveldata-cache and data-TLB 415, execution unit(s) 440, and portions ofout-of-order unit 435 are potentially fully shared.

Processor 400 often includes other resources, which may be fully shared,shared through partitioning, or dedicated by/to processing elements. InFIG. 4, an embodiment of a purely exemplary processor with illustrativelogical units/resources of a processor is illustrated. Note that aprocessor may include, or omit, any of these functional units, as wellas include any other known functional units, logic, or firmware notdepicted. As illustrated, core 401 includes a simplified, representativeout-of-order (000) processor core. But an in-order processor may beutilized in different embodiments. The 000 core includes a branch targetbuffer 420 to predict branches to be executed/taken and aninstruction-translation buffer (I-TLB) 420 to store address translationentries for instructions.

Core 401 further includes decode module 425 coupled to fetch unit 420 todecode fetched elements. Fetch logic, in one embodiment, includesindividual sequencers associated with thread slots 401 a, 401 b,respectively. Usually core 401 is associated with a first ISA, whichdefines/specifies instructions executable on processor 400. Oftenmachine code instructions that are part of the first ISA include aportion of the instruction (referred to as an opcode), whichreferences/specifies an instruction or operation to be performed. Decodelogic 425 includes circuitry that recognizes these instructions fromtheir opcodes and passes the decoded instructions on in the pipeline forprocessing as defined by the first ISA. For example, decoders 425, inone embodiment, include logic designed or adapted to recognize specificinstructions, such as transactional instruction. As a result of therecognition by decoders 425, the architecture or core 401 takesspecific, predefined actions to perform tasks associated with theappropriate instruction. It is important to note that any of the tasks,blocks, operations, and methods described herein may be performed inresponse to a single or multiple instructions; some of which may be newor old instructions.

In one example, allocator and renamer block 430 includes an allocator toreserve resources, such as register files to store instructionprocessing results. However, threads 401 a and 401 b are potentiallycapable of out-of-order execution, where allocator and renamer block 430also reserves other resources, such as reorder buffers to trackinstruction results. Unit 430 may also include a register renamer torename program/instruction reference registers to other registersinternal to processor 400. Reorder/retirement unit 435 includescomponents, such as the reorder buffers mentioned above, load buffers,and store buffers, to support out-of-order execution and later in-orderretirement of instructions executed out-of-order.

Scheduler and execution unit(s) block 440, in one embodiment, includes ascheduler unit to schedule instructions/operation on execution units.For example, a floating point instruction is scheduled on a port of anexecution unit that has an available floating point execution unit.Register files associated with the execution units are also included tostore information instruction processing results. Exemplary executionunits include a floating point execution unit, an integer executionunit, a jump execution unit, a load execution unit, a store executionunit, and other known execution units.

Lower level data cache and data translation buffer (D-TLB) 450 arecoupled to execution unit(s) 440. The data cache is to store recentlyused/operated on elements, such as data operands, which are potentiallyheld in memory coherency states. The D-TLB is to store recentvirtual/linear to physical address translations. As a specific example,a processor may include a page table structure to break physical memoryinto a plurality of virtual pages.

Here, cores 401 and 402 share access to higher-level or further-outcache 410, which is to cache recently fetched elements. Note thathigher-level or further-out refers to cache levels increasing or gettingfurther away from the execution unit(s). In one embodiment, higher-levelcache 410 is a last-level data cache—last cache in the memory hierarchyon processor 400—such as a second or third level data cache. However,higher level cache 410 is not so limited, as it may be associated withor includes an instruction cache. A trace cache—a type of instructioncache—instead may be coupled after decoder 425 to store recently decodedtraces.

In the depicted configuration, processor 400 also includes bus interfacemodule 405 and a power controller 460, which may perform powermanagement in accordance with an embodiment of the present invention. Inthis scenario, bus interface 405 is to communicate with devices externalto processor 400, such as system memory and other components.

A memory controller 470 may interface with other devices such as one ormany memories. In an example, bus interface 405 includes a ringinterconnect with a memory controller for interfacing with a memory anda graphics controller for interfacing with a graphics processor. In anSoC environment, even more devices, such as a network interface,coprocessors, memory, graphics processor, and any other known computerdevices/interface may be integrated on a single die or integratedcircuit to provide small form factor with high functionality and lowpower consumption.

Referring now to FIG. 5, shown is a block diagram of amicro-architecture of a processor core in accordance with one embodimentof the present invention. As shown in FIG. 5, processor core 500 may bea multi-stage pipelined out-of-order processor. Core 500 may operate atvarious voltages based on a received operating voltage, which may bereceived from an integrated voltage regulator or external voltageregulator.

As seen in FIG. 5, core 500 includes front end units 510, which may beused to fetch instructions to be executed and prepare them for use laterin the processor pipeline. For example, front end units 510 may includea fetch unit 501, an instruction cache 503, and an instruction decoder505. In some implementations, front end units 510 may further include atrace cache, along with microcode storage as well as a micro-operationstorage. Fetch unit 501 may fetch macro-instructions, e.g., from memoryor instruction cache 503, and feed them to instruction decoder 505 todecode them into primitives, i.e., micro-operations for execution by theprocessor.

Coupled between front end units 510 and execution units 520 is anout-of-order (000) engine 515 that may be used to receive themicro-instructions and prepare them for execution. More specifically 000engine 515 may include various buffers to re-order micro-instructionflow and allocate various resources needed for execution, as well as toprovide renaming of logical registers onto storage locations withinvarious register files such as register file 530 and extended registerfile 535. Register file 530 may include separate register files forinteger and floating point operations. For purposes of configuration,control, and additional operations, a set of machine specific registers(MSRs) 538 may also be present and accessible to various logic withincore 500 (and external to the core). For example, power limitinformation may be stored in one or more MSR and be dynamically updatedas described herein.

Various resources may be present in execution units 520, including, forexample, various integer, floating point, and single instructionmultiple data (SIMD) logic units, among other specialized hardware. Forexample, such execution units may include one or more arithmetic logicunits (ALUs) 522 and one or more vector execution units 524, among othersuch execution units.

Results from the execution units may be provided to retirement logic,namely a reorder buffer (ROB) 540. More specifically, ROB 540 mayinclude various arrays and logic to receive information associated withinstructions that are executed. This information is then examined by ROB540 to determine whether the instructions can be validly retired andresult data committed to the architectural state of the processor, orwhether one or more exceptions occurred that prevent a proper retirementof the instructions. Of course, ROB 540 may handle other operationsassociated with retirement.

As shown in FIG. 5, ROB 540 is coupled to a cache 550 which, in oneembodiment may be a low level cache (e.g., an L1 cache) although thescope of the present invention is not limited in this regard. Also,execution units 520 can be directly coupled to cache 550. From cache550, data communication may occur with higher level caches, systemmemory and so forth. While shown with this high level in the embodimentof FIG. 5, understand the scope of the present invention is not limitedin this regard. For example, while the implementation of FIG. 5 is withregard to an out-of-order machine such as of an Intel® x86 instructionset architecture (ISA), the scope of the present invention is notlimited in this regard. That is, other embodiments may be implemented inan in-order processor, a reduced instruction set computing (RISC)processor such as an ARM-based processor, or a processor of another typeof ISA that can emulate instructions and operations of a different ISAvia an emulation engine and associated logic circuitry.

Referring now to FIG. 6, shown is a block diagram of amicro-architecture of a processor core in accordance with anotherembodiment. In the embodiment of FIG. 6, core 600 may be a low powercore of a different micro-architecture, such as an Intel® Atom™-basedprocessor having a relatively limited pipeline depth designed to reducepower consumption. As seen, core 600 includes an instruction cache 610coupled to provide instructions to an instruction decoder 615. A branchpredictor 605 may be coupled to instruction cache 610. Note thatinstruction cache 610 may further be coupled to another level of a cachememory, such as an L2 cache (not shown for ease of illustration in FIG.6). In turn, instruction decoder 615 provides decoded instructions to anissue queue 620 for storage and delivery to a given execution pipeline.A microcode ROM 618 is coupled to instruction decoder 615.

A floating point pipeline 630 includes a floating point register file632 which may include a plurality of architectural registers of a givenbit with such as 128, 256 or 512 bits. Pipeline 630 includes a floatingpoint scheduler 634 to schedule instructions for execution on one ofmultiple execution units of the pipeline. In the embodiment shown, suchexecution units include an ALU 635, a shuffle unit 636, and a floatingpoint adder 638. In turn, results generated in these execution units maybe provided back to buffers and/or registers of register file 632. Ofcourse understand while shown with these few example execution units,additional or different floating point execution units may be present inanother embodiment.

An integer pipeline 640 also may be provided. In the embodiment shown,pipeline 640 includes an integer register file 642 which may include aplurality of architectural registers of a given bit with such as 128 or256 bits. Pipeline 640 includes an integer scheduler 644 to scheduleinstructions for execution on one of multiple execution units of thepipeline. In the embodiment shown, such execution units include an ALU645, a shifter unit 646, and a jump execution unit 648. In turn, resultsgenerated in these execution units may be provided back to buffersand/or registers of register file 642. Of course understand while shownwith these few example execution units, additional or different integerexecution units may be present in another embodiment.

A memory execution scheduler 650 may schedule memory operations forexecution in an address generation unit 652, which is also coupled to aTLB 654. As seen, these structures may couple to a data cache 660, whichmay be a L0 and/or L1 data cache that in turn couples to additionallevels of a cache memory hierarchy, including an L2 cache memory.

To provide support for out-of-order execution, an allocator/renamer 670may be provided, in addition to a reorder buffer 680, which isconfigured to reorder instructions executed out of order for retirementin order. Although shown with this particular pipeline architecture inthe illustration of FIG. 6, understand that many variations andalternatives are possible.

Note that in a processor having asymmetric cores, such as in accordancewith the micro-architectures of FIGS. 5 and 6, workloads may bedynamically swapped between the cores for power management reasons, asthese cores, although having different pipeline designs and depths, maybe of the same or related ISA. Such dynamic core swapping may beperformed in a manner transparent to a user application (and possiblykernel also).

Referring to FIG. 7, shown is a block diagram of a micro-architecture ofa processor core in accordance with yet another embodiment. Asillustrated in FIG. 7, a core 700 may include a multi-staged in-orderpipeline to execute at very low power consumption levels. As one suchexample, processor 700 may have a micro-architecture in accordance withan ARM Cortex A53 design available from ARM Holdings, LTD., Sunnyvale,Calif. In an implementation, an 8-stage pipeline may be provided that isconfigured to execute both 32-bit and 64-bit code. Core 700 includes afetch unit 710 that is configured to fetch instructions and provide themto a decode unit 715, which may decode the instructions, e.g.,macro-instructions of a given ISA such as an ARMv8 ISA. Note furtherthat a queue 730 may couple to decode unit 715 to store decodedinstructions. Decoded instructions are provided to an issue logic 725,where the decoded instructions may be issued to a given one of multipleexecution units.

With further reference to FIG. 7, issue logic 725 may issue instructionsto one of multiple execution units. In the embodiment shown, theseexecution units include an integer unit 735, a multiply unit 740, afloating point/vector unit 750, a dual issue unit 760, and a load/storeunit 770. The results of these different execution units may be providedto a writeback unit 780. Understand that while a single writeback unitis shown for ease of illustration, in some implementations separatewriteback units may be associated with each of the execution units.Furthermore, understand that while each of the units and logic shown inFIG. 7 is represented at a high level, a particular implementation mayinclude more or different structures. A processor designed using one ormore cores having a pipeline as in FIG. 7 may be implemented in manydifferent end products, extending from mobile devices to server systems.

Referring to FIG. 8, shown is a block diagram of a micro-architecture ofa processor core in accordance with a still further embodiment. Asillustrated in FIG. 8, a core 800 may include a multi-stage multi-issueout-of-order pipeline to execute at very high performance levels (whichmay occur at higher power consumption levels than core 700 of FIG. 7).As one such example, processor 800 may have a microarchitecture inaccordance with an ARM Cortex A57 design. In an implementation, a 15 (orgreater)-stage pipeline may be provided that is configured to executeboth 32-bit and 64-bit code. In addition, the pipeline may provide for 3(or greater)-wide and 3 (or greater)-issue operation. Core 800 includesa fetch unit 810 that is configured to fetch instructions and providethem to a decoder/renamer/dispatcher 815, which may decode theinstructions, e.g., macro-instructions of an ARMv8 instruction setarchitecture, rename register references within the instructions, anddispatch the instructions (eventually) to a selected execution unit.Decoded instructions may be stored in a queue 825. Note that while asingle queue structure is shown for ease of illustration in FIG. 8,understand that separate queues may be provided for each of the multipledifferent types of execution units.

Also shown in FIG. 8 is an issue logic 830 from which decodedinstructions stored in queue 825 may be issued to a selected executionunit. Issue logic 830 also may be implemented in a particular embodimentwith a separate issue logic for each of the multiple different types ofexecution units to which issue logic 830 couples.

Decoded instructions may be issued to a given one of multiple executionunits. In the embodiment shown, these execution units include one ormore integer units 835, a multiply unit 840, a floating point/vectorunit 850, a branch unit 860, and a load/store unit 870. In anembodiment, floating point/vector unit 850 may be configured to handleSIMD or vector data of 128 or 256 bits. Still further, floatingpoint/vector execution unit 850 may perform IEEE-754 double precisionfloating-point operations. The results of these different executionunits may be provided to a writeback unit 880. Note that in someimplementations separate writeback units may be associated with each ofthe execution units. Furthermore, understand that while each of theunits and logic shown in FIG. 8 is represented at a high level, aparticular implementation may include more or different structures.

Note that in a processor having asymmetric cores, such as in accordancewith the micro-architectures of FIGS. 7 and 8, workloads may bedynamically swapped for power management reasons, as these cores,although having different pipeline designs and depths, may be of thesame or related ISA. Such dynamic core swapping may be performed in amanner transparent to a user application (and possibly kernel also).

A processor designed using one or more cores having pipelines as in anyone or more of FIGS. 5-8 may be implemented in many different endproducts, extending from mobile devices to server systems. Referring nowto FIG. 9, shown is a block diagram of a processor in accordance withanother embodiment of the present invention. In the embodiment of FIG.9, processor 900 may be a SoC including multiple domains, each of whichmay be controlled to operate at an independent operating voltage andoperating frequency. As a specific illustrative example, processor 900may be an Intel® Architecture Core™-based processor such as an i3, i5,i7 or another such processor available from Intel Corporation. However,other low power processors such as available from Advanced MicroDevices, Inc. (AMD) of Sunnyvale, Calif., an ARM-based design from ARMHoldings, Ltd. or licensee thereof or a MIPS-based design from MIPSTechnologies, Inc. of Sunnyvale, Calif., or their licensees or adoptersmay instead be present in other embodiments such as an Apple A7processor, a Qualcomm Snapdragon processor, or Texas Instruments OMAPprocessor. Such SoC may be used in a low power system such as asmartphone, tablet computer, phablet computer, Ultrabook™ computer orother portable computing device.

In the high level view shown in FIG. 9, processor 900 includes aplurality of core units 910 ₀-910 _(n). Each core unit may include oneor more processor cores, one or more cache memories and other circuitry.Each core unit 910 may support one or more instructions sets (e.g., an86 instruction set (with some extensions that have been added with newerversions); a MIPS instruction set; an ARM instruction set (with optionaladditional extensions such as NEON)) or other instruction set orcombinations thereof. Note that some of the core units may beheterogeneous resources (e.g., of a different design). In addition, eachsuch core may be coupled to a cache memory (not shown) which in anembodiment may be a shared level (L2) cache memory. A non-volatilestorage 930 may be used to store various program and other data. Forexample, this storage may be used to store at least portions ofmicrocode, boot information such as a BIOS, other system software or soforth.

Each core unit 910 may also include an interface such as a bus interfaceunit to enable interconnection to additional circuitry of the processor.In an embodiment, each core unit 910 couples to a coherent fabric thatmay act as a primary cache coherent on-die interconnect that in turncouples to a memory controller 935. In turn, memory controller 935controls communications with a memory such as a DRAM (not shown for easeof illustration in FIG. 9).

In addition to core units, additional processing engines are presentwithin the processor, including at least one graphics unit 920 which mayinclude one or more graphics processing units (GPUs) to perform graphicsprocessing as well as to possibly execute general purpose operations onthe graphics processor (so-called GPGPU operation). In addition, atleast one image signal processor 925 may be present. Signal processor925 may be configured to process incoming image data received from oneor more capture devices, either internal to the SoC or off-chip.

Other accelerators also may be present. In the illustration of FIG. 9, avideo coder 950 may perform coding operations including encoding anddecoding for video information, e.g., providing hardware accelerationsupport for high definition video content. A display controller 955further may be provided to accelerate display operations includingproviding support for internal and external displays of a system. Inaddition, a security processor 945 may be present to perform securityoperations such as secure boot operations, various cryptographyoperations and so forth.

Each of the units may have its power consumption controlled via a powermanager 940, which may include control logic to perform the variouspower management techniques described herein.

In some embodiments, SoC 900 may further include a non-coherent fabriccoupled to the coherent fabric to which various peripheral devices maycouple. One or more interfaces 960 a-960 d enable communication with oneor more off-chip devices. Such communications may be via a variety ofcommunication protocols such as PCIe™, GPIO, USB, I²C, UART, MIPI, SDIO,DDR, SPI, HDMI, among other types of communication protocols. Althoughshown at this high level in the embodiment of FIG. 9, understand thescope of the present invention is not limited in this regard.

Referring now to FIG. 10, shown is a block diagram of a representativeSoC. In the embodiment shown, SoC 1000 may be a multi-core SoCconfigured for low power operation to be optimized for incorporationinto a smartphone or other low power device such as a tablet computer orother portable computing device. As an example, SoC 1000 may beimplemented using asymmetric or different types of cores, such ascombinations of higher power and/or low power cores, e.g., out-of-ordercores and in-order cores. In different embodiments, these cores may bebased on an Intel® Architecture™ core design or an ARM architecturedesign. In yet other embodiments, a mix of Intel and ARM cores may beimplemented in a given SoC.

As seen in FIG. 10, SoC 1000 includes a first core domain 1010 having aplurality of first cores 1012 ₀-1012 ₃. In an example, these cores maybe low power cores such as in-order cores. In one embodiment these firstcores may be implemented as ARM Cortex A53 cores. In turn, these corescouple to a cache memory 1015 of core domain 1010. In addition, SoC 1000includes a second core domain 1020. In the illustration of FIG. 10,second core domain 1020 has a plurality of second cores 1022 ₀-1022 ₃.In an example, these cores may be higher power-consuming cores thanfirst cores 1012. In an embodiment, the second cores may be out-of-ordercores, which may be implemented as ARM Cortex A57 cores. In turn, thesecores couple to a cache memory 1025 of core domain 1020. Note that whilethe example shown in FIG. 10 includes 4 cores in each domain, understandthat more or fewer cores may be present in a given domain in otherexamples.

With further reference to FIG. 10, a graphics domain 1030 also isprovided, which may include one or more graphics processing units (GPUs)configured to independently execute graphics workloads, e.g., providedby one or more cores of core domains 1010 and 1020. As an example, GPUdomain 1030 may be used to provide display support for a variety ofscreen sizes, in addition to providing graphics and display renderingoperations.

As seen, the various domains couple to a coherent interconnect 1040,which in an embodiment may be a cache coherent interconnect fabric thatin turn couples to an integrated memory controller 1050. Coherentinterconnect 1040 may include a shared cache memory, such as an L3cache, in some examples. In an embodiment, memory controller 1050 may bea direct memory controller to provide for multiple channels ofcommunication with an off-chip memory, such as multiple channels of aDRAM (not shown for ease of illustration in FIG. 10).

In different examples, the number of the core domains may vary. Forexample, for a low power SoC suitable for incorporation into a mobilecomputing device, a limited number of core domains such as shown in FIG.10 may be present. Still further, in such low power SoCs, core domain1020 including higher power cores may have fewer numbers of such cores.For example, in one implementation two cores 1022 may be provided toenable operation at reduced power consumption levels. In addition, thedifferent core domains may also be coupled to an interrupt controller toenable dynamic swapping of workloads between the different domains.

In yet other embodiments, a greater number of core domains, as well asadditional optional IP logic may be present, in that an SoC can bescaled to higher performance (and power) levels for incorporation intoother computing devices, such as desktops, servers, high performancecomputing systems, base stations forth. As one such example, 4 coredomains each having a given number of out-of-order cores may beprovided. Still further, in addition to optional GPU support (which asan example may take the form of a GPGPU), one or more accelerators toprovide optimized hardware support for particular functions (e.g. webserving, network processing, switching or so forth) also may beprovided. In addition, an input/output interface may be present tocouple such accelerators to off-chip components.

Referring now to FIG. 11, shown is a block diagram of another exampleSoC. In the embodiment of FIG. 11, SoC 1100 may include variouscircuitry to enable high performance for multimedia applications,communications and other functions. As such, SoC 1100 is suitable forincorporation into a wide variety of portable and other devices, such assmartphones, tablet computers, smart TVs and so forth. In the exampleshown, SoC 1100 includes a central processor unit (CPU) domain 1110. Inan embodiment, a plurality of individual processor cores may be presentin CPU domain 1110. As one example, CPU domain 1110 may be a quad coreprocessor having 4 multithreaded cores. Such processors may behomogeneous or heterogeneous processors, e.g., a mix of low power andhigh power processor cores.

In turn, a GPU domain 1120 is provided to perform advanced graphicsprocessing in one or more GPUs to handle graphics and compute APIs. ADSP unit 1130 may provide one or more low power DSPs for handlinglow-power multimedia applications such as music playback, audio/videoand so forth, in addition to advanced calculations that may occur duringexecution of multimedia instructions. In turn, a communication unit 1140may include various components to provide connectivity via variouswireless protocols, such as cellular communications (including 3G/4GLTE), wireless local area protocols such as Bluetooth™ IEEE 802.11, andso forth.

Still further, a multimedia processor 1150 may be used to performcapture and playback of high definition video and audio content,including processing of user gestures. A sensor unit 1160 may include aplurality of sensors and/or a sensor controller to interface to variousoff-chip sensors present in a given platform. An image signal processor1170 may be provided with one or more separate ISPs to perform imageprocessing with regard to captured content from one or more cameras of aplatform, including still and video cameras.

A display processor 1180 may provide support for connection to a highdefinition display of a given pixel density, including the ability towirelessly communicate content for playback on such display. Stillfurther, a location unit 1190 may include a GPS receiver with supportfor multiple GPS constellations to provide applications highly accuratepositioning information obtained using as such GPS receiver. Understandthat while shown with this particular set of components in the exampleof FIG. 11, many variations and alternatives are possible.

Referring now to FIG. 12, shown is a block diagram of an example systemwith which embodiments can be used. As seen, system 1200 may be asmartphone or other wireless communicator. A baseband processor 1205 isconfigured to perform various signal processing with regard tocommunication signals to be transmitted from or received by the system.In turn, baseband processor 1205 is coupled to an application processor1210, which may be a main CPU of the system to execute an OS and othersystem software, in addition to user applications such as manywell-known social media and multimedia apps. Application processor 1210may further be configured to perform a variety of other computingoperations for the device.

In turn, application processor 1210 can couple to a userinterface/display 1220, e.g., a touch screen display. In addition,application processor 1210 may couple to a memory system including anon-volatile memory, namely a flash memory 1230 and a system memory,namely a dynamic random access memory (DRAM) 1235. As further seen,application processor 1210 further couples to a capture device 1240 suchas one or more image capture devices that can record video and/or stillimages.

Still referring to FIG. 12, a universal integrated circuit card (UICC)1240 comprising a subscriber identity module and possibly a securestorage and cryptoprocessor is also coupled to application processor1210. System 1200 may further include a security processor 1250 that maycouple to application processor 1210. A plurality of sensors 1225 maycouple to application processor 1210 to enable input of a variety ofsensed information such as accelerometer and other environmentalinformation. An audio output device 1295 may provide an interface tooutput sound, e.g., in the form of voice communications, played orstreaming audio data and so forth.

As further illustrated, a near field communication (NFC) contactlessinterface 1260 is provided that communicates in a NFC near field via anNFC antenna 1265. While separate antennae are shown in FIG. 12,understand that in some implementations one antenna or a different setof antennae may be provided to enable various wireless functionality.

A power management integrated circuit (PMIC) 1215 couples to applicationprocessor 1210 to perform platform level power management. To this end,PMIC 1215 may issue power management requests to application processor1210 to enter certain low power states as desired. Furthermore, based onplatform constraints, PMIC 1215 may also control the power level ofother components of system 1200.

To enable communications to be transmitted and received, variouscircuitry may be coupled between baseband processor 1205 and an antenna1290. Specifically, a radio frequency (RF) transceiver 1270 and awireless local area network (WLAN) transceiver 1275 may be present. Ingeneral, RF transceiver 1270 may be used to receive and transmitwireless data and calls according to a given wireless communicationprotocol such as 3G or 4G wireless communication protocol such as inaccordance with a code division multiple access (CDMA), global systemfor mobile communication (GSM), long term evolution (LTE) or otherprotocol. In addition a GPS sensor 1280 may be present. Other wirelesscommunications such as receipt or transmission of radio signals, e.g.,AM/FM and other signals may also be provided. In addition, via WLANtransceiver 1275, local wireless communications can also be realized.

Referring now to FIG. 13, shown is a block diagram of another examplesystem with which embodiments may be used. In the illustration of FIG.13, system 1300 may be mobile low-power system such as a tabletcomputer, 2:1 tablet, phablet or other convertible or standalone tabletsystem. As illustrated, a SoC 1310 is present and may be configured tooperate as an application processor for the device.

A variety of devices may couple to SoC 1310. In the illustration shown,a memory subsystem includes a flash memory 1340 and a DRAM 1345 coupledto SoC 1310. In addition, a touch panel 1320 is coupled to the SoC 1310to provide display capability and user input via touch, includingprovision of a virtual keyboard on a display of touch panel 1320. Toprovide wired network connectivity, SoC 1310 couples to an Ethernetinterface 1330. A peripheral hub 1325 is coupled to SoC 1310 to enableinterfacing with various peripheral devices, such as may be coupled tosystem 1300 by any of various ports or other connectors.

In addition to internal power management circuitry and functionalitywithin SoC 1310, a PMIC 1380 is coupled to SoC 1310 to provideplatform-based power management, e.g., based on whether the system ispowered by a battery 1390 or AC power via an AC adapter 1395. Inaddition to this power source-based power management, PMIC 1380 mayfurther perform platform power management activities based onenvironmental and usage conditions. Still further, PMIC 1380 maycommunicate control and status information to SoC 1310 to cause variouspower management actions within SoC 1310.

Still referring to FIG. 13, to provide for wireless capabilities, a WLANunit 1350 is coupled to SoC 1310 and in turn to an antenna 1355. Invarious implementations, WLAN unit 1350 may provide for communicationaccording to one or more wireless protocols.

As further illustrated, a plurality of sensors 1360 may couple to SoC1310. These sensors may include various accelerometer, environmental andother sensors, including user gesture sensors. Finally, an audio codec1365 is coupled to SoC 1310 to provide an interface to an audio outputdevice 1370. Of course understand that while shown with this particularimplementation in FIG. 13, many variations and alternatives arepossible.

Referring now to FIG. 14, shown is a block diagram of a representativecomputer system such as notebook, Ultrabook™ or other small form factorsystem. A processor 1410, in one embodiment, includes a microprocessor,multi-core processor, multithreaded processor, an ultra low voltageprocessor, an embedded processor, or other known processing element. Inthe illustrated implementation, processor 1410 acts as a main processingunit and central hub for communication with many of the variouscomponents of the system 1400. As one example, processor 1400 isimplemented as a SoC.

Processor 1410, in one embodiment, communicates with a system memory1415. As an illustrative example, the system memory 1415 is implementedvia multiple memory devices or modules to provide for a given amount ofsystem memory.

To provide for persistent storage of information such as data,applications, one or more operating systems and so forth, a mass storage1420 may also couple to processor 1410. In various embodiments, toenable a thinner and lighter system design as well as to improve systemresponsiveness, this mass storage may be implemented via a SSD or themass storage may primarily be implemented using a hard disk drive (HDD)with a smaller amount of SSD storage to act as a SSD cache to enablenon-volatile storage of context state and other such information duringpower down events so that a fast power up can occur on re-initiation ofsystem activities. Also shown in FIG. 14, a flash device 1422 may becoupled to processor 1410, e.g., via a serial peripheral interface(SPI). This flash device may provide for non-volatile storage of systemsoftware, including a basic input/output software (BIOS) as well asother firmware of the system.

Various input/output (I/O) devices may be present within system 1400.Specifically shown in the embodiment of FIG. 14 is a display 1424 whichmay be a high definition LCD or LED panel that further provides for atouch screen 1425. In one embodiment, display 1424 may be coupled toprocessor 1410 via a display interconnect that can be implemented as ahigh performance graphics interconnect. Touch screen 1425 may be coupledto processor 1410 via another interconnect, which in an embodiment canbe an I²C interconnect. As further shown in FIG. 14, in addition totouch screen 1425, user input by way of touch can also occur via a touchpad 1430 which may be configured within the chassis and may also becoupled to the same I²C interconnect as touch screen 1425.

For perceptual computing and other purposes, various sensors may bepresent within the system and may be coupled to processor 1410 indifferent manners. Certain inertial and environmental sensors may coupleto processor 1410 through a sensor hub 1440, e.g., via an I²Cinterconnect. In the embodiment shown in FIG. 14, these sensors mayinclude an accelerometer 1441, an ambient light sensor (ALS) 1442, acompass 1443 and a gyroscope 1444. Other environmental sensors mayinclude one or more thermal sensors 1446 which in some embodimentscouple to processor 1410 via a system management bus (SMBus) bus.

Also seen in FIG. 14, various peripheral devices may couple to processor1410 via a low pin count (LPC) interconnect. In the embodiment shown,various components can be coupled through an embedded controller 1435.Such components can include a keyboard 1436 (e.g., coupled via a PS2interface), a fan 1437, and a thermal sensor 1439. In some embodiments,touch pad 1430 may also couple to EC 1435 via a PS2 interface. Inaddition, a security processor such as a trusted platform module (TPM)1438 may also couple to processor 1410 via this LPC interconnect.

System 1400 can communicate with external devices in a variety ofmanners, including wirelessly. In the embodiment shown in FIG. 14,various wireless modules, each of which can correspond to a radioconfigured for a particular wireless communication protocol, arepresent. One manner for wireless communication in a short range such asa near field may be via a NFC unit 1445 which may communicate, in oneembodiment with processor 1410 via an SMBus. Note that via this NFC unit1445, devices in close proximity to each other can communicate.

As further seen in FIG. 14, additional wireless units can include othershort range wireless engines including a WLAN unit 1450 and a Bluetoothunit 1452. Using WLAN unit 1450, Wi-Fi™ communications can be realized,while via Bluetooth unit 1452, short range Bluetooth™ communications canoccur. These units may communicate with processor 1410 via a given link.

In addition, wireless wide area communications, e.g., according to acellular or other wireless wide area protocol, can occur via a WWAN unit1456 which in turn may couple to a subscriber identity module (SIM)1457. In addition, to enable receipt and use of location information, aGPS module 1455 may also be present. Note that in the embodiment shownin FIG. 14, WWAN unit 1456 and an integrated capture device such as acamera module 1454 may communicate via a given link.

An integrated camera module 1454 can be incorporated in the lid. Toprovide for audio inputs and outputs, an audio processor can beimplemented via a digital signal processor (DSP) 1460, which may coupleto processor 1410 via a high definition audio (HDA) link. Similarly, DSP1460 may communicate with an integrated coder/decoder (CODEC) andamplifier 1462 that in turn may couple to output speakers 1463 which maybe implemented within the chassis. Similarly, amplifier and CODEC 1462can be coupled to receive audio inputs from a microphone 1465 which inan embodiment can be implemented via dual array microphones (such as adigital microphone array) to provide for high quality audio inputs toenable voice-activated control of various operations within the system.Note also that audio outputs can be provided from amplifier/CODEC 1462to a headphone jack 1464. Although shown with these particularcomponents in the embodiment of FIG. 14, understand the scope of thepresent invention is not limited in this regard.

Embodiments may be implemented in many different system types. Referringnow to FIG. 15, shown is a block diagram of a system in accordance withan embodiment of the present invention. As shown in FIG. 15,multiprocessor system 1500 is a point-to-point interconnect system, andincludes a first processor 1570 and a second processor 1580 coupled viaa point-to-point interconnect 1550. As shown in FIG. 15, each ofprocessors 1570 and 1580 may be multicore processors, including firstand second processor cores (i.e., processor cores 1574 a and 1574 b andprocessor cores 1584 a and 1584 b), although potentially many more coresmay be present in the processors. Each of the processors can include aPCU or other power management logic to perform processor-based powermanagement as described herein.

Still referring to FIG. 15, first processor 1570 further includes amemory controller hub (MCH) 1572 and point-to-point (P-P) interfaces1576 and 1578. Similarly, second processor 1580 includes a MCH 1582 andP-P interfaces 1586 and 1588. As shown in FIG. 15, MCH's 1572 and 1582couple the processors to respective memories, namely a memory 1532 and amemory 1534, which may be portions of system memory (e.g., DRAM) locallyattached to the respective processors. First processor 1570 and secondprocessor 1580 may be coupled to a chipset 1590 via P-P interconnects1562 and 1564, respectively. As shown in FIG. 15, chipset 1590 includesP-P interfaces 1594 and 1598.

Furthermore, chipset 1590 includes an interface 1592 to couple chipset1590 with a high performance graphics engine 1538, by a P-P interconnect1539. In turn, chipset 1590 may be coupled to a first bus 1516 via aninterface 1596. As shown in FIG. 15, various input/output (I/O) devices1514 may be coupled to first bus 1516, along with a bus bridge 1518which couples first bus 1516 to a second bus 1520. Various devices maybe coupled to second bus 1520 including, for example, a keyboard/mouse1522, communication devices 1526 and a data storage unit 1528 such as adisk drive or other mass storage device which may include code 1530, inone embodiment. Further, an audio I/O 1524 may be coupled to second bus1520. Embodiments can be incorporated into other types of systemsincluding mobile devices such as a smart cellular telephone, tabletcomputer, netbook, Ultrabook™, or so forth.

A processor may have a central reset and power management unit (PMU)that may include firmware (“pCode” herein) that can be patched, e.g.,portions of the pCode can be added or removed from execution. A patchscheme for the pCode, e.g., to indicate which portions are to beexecuted and which portions are to be removed from execution, may bedetermined by a programming entity.

A PMA (Power Management Agent) is typically a hardware unit that may beimplemented in blocks that perform self-contained power managementactions (also “hooks” herein) such as power reset, clock reset,configuration, save/restore ability, etc. The PMU and the PMA maysupport a high-level command/acknowledgment protocol for powermanagement flows such as sleep states (e.g., C-states), transition of acore within the processor to a reduced activity state (e.g., via changein clock frequency, operating voltage, etc.), reset, etc.

Some benefits of a PMA include simplification of the PMU and pCode bymovement of specific hooks to a specific block, ability to implement andvalidate the PMU, and placement of a block in an environment that isisolated from other portions of a processor and enables changes to beimplemented independently of the other portions.

Use of PMA instead of central implementation in the PMU may result inloss of ability to fix and change work flow via, e.g., one or more pCodepatches. This ability may be important, e.g., for reset and powermanagement features in order to improve chip survivability, e.g., duringan initial debug phase of the processor. Further, the ability to changeone or more portions of the operations to be executed can enable finetuning of power/performance in a later phase of production of theprocessor.

In embodiments, a programmable (“patchable”) PMA may enableimplementation of the PMA in hardware, maintain advantages of the PMA(e.g., simplification, isolation), and also maintain a flexibility of apCode implementation, e.g., enable change in the operation set to beexecuted by the PMA. Additionally, the patchable PMA can enableselection of various reset and power management flows using one (ormore) finite state machine(s) (FSM(s)). For example, in some casesdifferent flows (a flow may also be referred to as a sequence herein)are similar to each other, with only slight differences between them,e.g. C-state exit and power reduction transition/exit are variations ofa power up flow, while reset-warn, C-State entry and power reductiontransition/entry of a core are variations of a power down flow.

In embodiments, the patchable PMA may be implemented by expressingvarious flows, e.g., reset flows and power management flows, e.g., intooperations to be implemented/executed by hardware, and by inclusion of aset of control registers that can enable/disable specific operations,change an order of operations, insert breakpoints, and permit furthercontrol options.

A legacy hardware PMA may lack controllability of the patchable PMA. Thepatchable PMA can be programmed to different behaviors using e.g., apCode patch, or test access point (TAP). In contrast to legacy hardwarePMA, in the patchable PMA pre-defined breakpoints may not be necessaryfor debugging since breakpoints can be added via setting values in thecontrol registers. Simplification of implementation of several operationflows using a single table may enable implementation of several flowvariations easily in a short time.

In the patchable PMA we can define a super-set of all power up and powerdown operations, and a subset of the super-set can be specified for eachflow. The super-set may be defined in a static table (e.g. a table thatincludes permanently stored operations such as a hard wired table). Whenthe PMU instructs the PMA to issue a specific flow, a correspondingsubset of operations may be loaded into an internal register and the FSMmay be triggered according to the subset of operations.

In embodiments, “patch-ability” may be achieved via a control registerthat stores a set of indicators that includes an indicator (e.g., a bit)for each of the operations in a power up flow or a power down flow. Theindicator may indicate whether the corresponding operation to accomplisha particular function is to be executed in a particular subset, e.g., aselected flow.

In an embodiment, for each operation of the selected flow a pCode patchcan write a corresponding enable indicator into a respective storagelocation within an internal register, e.g., each storage location maycorrespond to an operation of the super-set. The PMA can execute thoseoperations of the selected flow that are enabled by the enableindicator. For example, the control register contents can enable one ormore of the following patching options: insert a breakpoint betweenoperations; change an order of operations; run in a single-operationmode; avoid specific operations; implement a new flow for a new feature;and combinations thereof.

In another embodiment, the pCode patch can write an “override flow” intolocations of an internal register. The pCode patch is to instruct thePMA to execute operations according to the override flow instead ofaccording to the selected flow.

FIG. 16 is a block diagram of a system 1600, according to embodiments ofthe present invention. System 1600 includes a processor 1610 and adynamic random access memory (DRAM) 1630, which may be an embedded DRAM(EDRAM), e.g., included in the same chip as the processor 1610. Theprocessor 1610 includes one or more cores 1602, (i=1, N), a centralreset and power management unit (PMU) 1620, cache memory 1660,interconnect logic 1670, and may include other logics, storage, etc.(not shown). The PMU 1620 includes pCode logic 1622 and may includeother logics, storage, etc. (not shown).

Shown in core 1602, is a power management agent (PMA) 1650, whichincludes static table 1612 and control register 1614.

The DRAM 1630 includes PMA 1632, which includes static table 1634 andcontrol register 1636. The static table 1634 includes a super-set ofoperations and a plurality of flow columns, each flow column tocorrespond to a flow. Each flow column is to indicate which operationsof the super-set are to be performed for the corresponding flow. In oneembodiment, the operations are permanently stored (e.g., hard wired)into the static table 1634.

In operation, the PMU 1620 may decide to effect a change in operation ofcore 1602 ₁, e.g., reduction in power consumption of the core 1602 ₁ asa result of a reduced processor load. The PMU 1620 may send to executionlogic 1616 of the PMA 1650 a command to execute a flow to reduce anactivity level of the core 1602 ₁, and a particular flow may be selectedby the PMA 1650 to be executed by the execution logic 1616. The pCodelogic 1622 may transmit a set of override values to an override controlregister 1614, each override value to correspond to a respectiveoperation of the selected flow. The override values may be dynamically(e.g., replaceably) stored, e.g., values to be stored in the controlregister 1614 at a time may be replaced at another time with differentoverride values. Dynamic storage may be contrasted with static storage,in which a stored value is to remain in storage (e.g., irreplaceable).

For each operation of the flow to be executed (as indicated by thecorresponding flow column), the execution logic 1616 may read thecontents of the corresponding override value stored in the overridecontrol register 1614. The override value may determine whether toexecute the operation or to skip the corresponding operation andcontinue to the next consecutive operation in the subset. When alloperations of the subset have been either executed or skipped, the PMA1650 becomes idle.

In another embodiment, pCode logic 1622 may store a set of overridevalues to the override control register (also “override column”) 1614,each override value to correspond to a respective operation of the flow.The override column may constitute an alternate flow, e.g., set ofindicators that indicate which operations are to be performed. Theoverride column may be executed instead of the selected flow column byexecution of each operation whose corresponding indicator in theoverride column indicates inclusion into the alternate flow.

With regard to the DRAM 1630, the PMU 1620 may determine a powerconsumption level for the DRAM 1630 (e.g., based on accesses to the DRAM1630), and the PMU 1620 may issue a command to the PMA 1632 in DRAM 1630to change a current power consumption level of the DRAM 1630, e.g.,clock frequency of the DRAM 1630. The PMA 1632 may select a subset ofoperations (e.g., by selection of a column) within register 1634 to beexecuted by execution logic 1638. The pCode logic 1622 may transmit aset of override values to an override to override control register 1636,each override value to correspond to a respective operation of thesubset of operations. For each operation to be executed, the executionlogic 1638 may read the contents of the corresponding override valuestored in the override control register 1636, which may determinewhether to execute the operation or to skip the operation and continueto the next consecutive operation in the subset. When all operations ofthe subset have been either executed or skipped, the PMA 1632 becomesidle.

Through use of override values in the override CR 1614 of the PMA 1650or the override CR 1636 of the PMA 1632, a flow of operations can bemodified to include or exclude individual operations, add breakpoints,change an order of execution of operations, etc.

FIG. 17 is a block diagram 1700 of a portion of a PMA, according to anembodiment of the present invention. The example shown may be animplementation of a patchable PMA for EDRAM integration. The PMA may beresponsible for reset and power management the EDRAM die, the CPU'sblocks that are involved in EDRAM integration as the cache controllerand On-Package I/O (OPIO), and external VRs. Table 1702 displays only aportion of each of several flows (e.g., 1712, 1714, 1716, 1718, and1720). There may be many more operations, and additional flows that canbe selected by, e.g., a PMU of a processor coupled to the EDRAM. OtherPMAs may include different operations of one or more flows to beexecuted by the PMA, e.g., to control power variables of a core of aprocessor when the PMA is within in the core.

Static table 1702 (e.g., hardwired) stores a super-set of operations1710. Also stored in the static table 1702 is a plurality of flows,e.g., each flow stored a respective one of columns 1712, 1714, 1716,1718, 1720, or additional columns (not shown). An override column 1722is to contain override values that may be provided by pCode logic, e.g.pCode logic 122 of FIG. 1. In some embodiments, override values may bedetermined based on user input, e.g., low use of the processor by theuser may cause cores to be placed in a sleep mode or low power usagemode. Values in column 1722 may be changed dynamically, e.g., based onvalues received that may vary for each instance of a call to execute aflow.

In operation, a flow may be selected by a PCU command register in orderto effect a change, e.g., power consumed, and an indication of selectionof a flow column may be sent via a path 1740 to a flow multiplexer(“mux”) 1730. The flow mux 1730 may read contents of the selected flowcolumn (e.g., one of 1712, 1714, 1716, 1718, or 1720) that correspondsto the selection received via path 1740. The flow mux 1730 may also readcontents of the override column 1722, and each stored value in theoverride column 1722 is to indicate whether or not a correspondingoperation of the selected flow column is to be executed. The flow mux1730 may determine which operations to send to execution logic to beexecuted based on the contents of the override column 1722.

In some embodiments, the override column 1722 may be populated (from thePCU command register) with values that define an alternate flow to beexecuted instead of one of the flows represented in one of the flowcolumns 1712, 1714, 1716, 1718, or 1720. For example, the contents ofthe override column 1722 may represent an update to contents of the flowcolumn that corresponds to the requested change (e.g., change in powerconsumed), and the contents of the override column 1722 (e.g.,operations to be executed according to the override column 1722) may beexecuted instead of the flow column. The flow mux 1730 receive aselection of column 1722 and may read contents of the override column1722 instead of the flow column that corresponds to the requestedchange, and may cause the execution logic to execute those operationsindicated in the override column 1722. For example, the contents of theoverride column 1722 may also determine, e.g., addition of one or morebreakpoints into the selected flow.

In an embodiment, an order of execution of the operations may bechanged, e.g., via multiple passes of a particular flow with each passhaving a different set of contents of the override column 1722. Forexample, to switch the order of execution of operations (as numbered incolumn 1702) from 1, 2, 3, 4, 5, 6, 7, etc. to 1, 3, 2, 4, 5, 6, 7, etc.in a first pass of the flow the corresponding override column caninclude the contents: 1,0,1,0,0,0,0 . . . , and in a second pass theoverride column can include the contents 0,1,0,1,1,1,1, . . . . Theoutput of operations of the first pass is 1, 3, with no furtheroperations until second pass. The output of operations of the secondpass is 2, 4, 5, 6, 7, etc. Hence consecutive passes of the same flowwith different override column contents can result in an order ofoperations 1,3,2,4,5,6,7, . . . .

As an example, an embedded DRAM (EDRAIVI) includes a PMA that is toreceive commands from a PMU of a processor. The PMA receives a commandto turn the EDRAM from an “off' state to an “on” state (e.g., viaexecution of flow 1716). However, a change in an order of flow ofoperations to a modified flow is requested from the PMU, e.g., “enableexternal VR” is to be executed prior to “enable clock distribution.” Fora first pass of flow execution, column 1722 can be populated as follows:CR(1)=0, CR(2)=1, CR(i)=0 (i=3-N), and when column 1716 is to beexecuted by execution logic, each operation that has a ‘1’ in column1716 is to be executed provided a ‘1’ is in the corresponding overridestorage location.

During the first pass, a first operation, “enable clock distribution,”has a ‘1’ stored in a corresponding location of column 1716; however, CR(1) stores a ‘0’, and therefore ‘enable clock distribution” will not beexecuted. A second operation, “enable external VR” has a ‘1’ stored in acorresponding location of column 1716 and CR (2) stores a ‘1’; therefore‘enable clock distribution” will be executed. For CR (i), (i=3 to N),the stored values are ‘0’, and therefore no other operations of theoff>on flow 1716 will be executed during the first pass.

In a second pass through the operations of the off>on flow, column 1722can be populated as follows: CR(1)=1, CR(2)=0, CR(i)=1 (i=3 to N). Anexecution of the second pass results in execution of “enable clockdistribution.” The second operation, “enable external VR” has a ‘1’stored in a corresponding location of column 1716; however, CR (2)stores a ‘0’, and therefore ‘enable clock distribution” will not beexecuted. For CR (i), (i=3 to N), the stored values are ‘1’, and eachoperation that has a ‘1’ stored in a corresponding location of theoff>on column will be executed during the second pass.

A result of execution of the first pass and the second pass is that“enable external VR” is executed and is followed by “enable clockdistribution,” e.g., the order of the modified flow.

FIG. 18 is a flow diagram of a method 1800, according to an embodimentof the present invention. Beginning at decision diamond 1810, if no flowselection is received by a PMA of a processor (e.g., PMA within a coreof the processor) from e.g., a PMU of the processor, continuing to block1820 the PMA is idle. If a flow selection is received, advancing todecision diamond 1830, if a first operation is enabled, e.g., asindicated by a corresponding override value in an override controlregister, advancing to block 1840 the first operation is performed andthe method proceeds to decision diamond 1850. If the first operation isnot enabled, as determined from contents of corresponding overridecontrol register, proceeding to decision diamond 1850, if operation 2 isenabled moving to block 1860 operation 2 is performed.

Each override is to determine whether the corresponding operation is tobe performed or skipped. For a flow of N operations, at decision diamond1870 if operation N is enabled as determined by contents of acorresponding override control register, continuing to block 1880,operation N is performed. After operation N is considered, e.g., eitherexecuted at block 1880 or skipped, returning to decision diamond 1810 ifa new flow selection is received the method advances to decision diamond1830. If no new flow selection is received, proceeding to block 1820 thePMA idles until a next flow selection is received.

FIG. 19 is a flow diagram of a method, according to another embodimentof the present invention. Method 1900 begins at block 1910, where apower management agent (PMA) of a core of a processor receives, frome.g., a power management unit (PMU) of the processor, an indication tochange power consumption of the core. Continuing to decision diamond1912, if there are no override values to be received from the PMU,advancing to block 1916 a power change flow, e.g., a subset ofoperations stored in a static table, is executed by the PMA. If the PMUhas override values to be stored in the PMA, advancing from decisiondiamond 1912 to block 1914, the PMA stores the override values intostorage locations of an override column in a control register of thePMA.

Moving to block 1918, an index i is set equal to zero. Proceeding toblock 1920, the index i is incremented. Continuing to decision diamond1922, if i>N all operations of the flow have been executed and advancingto block 1930 the method ends.

If i≦N, where N is a total number of operations (super-set) in thestatic table, advancing to decision diamond 1924 if the power changeflow includes the i^(th) operation of the static table, the methodproceeds to decision diamond 1926. At decision diamond 1926, if anoverride entry that corresponds to the i^(th) operation indicates thatthe i^(th) operation is to be executed, continuing to block 1928 the PMAexecutes the i^(th) operation.

If at decision diamond 1924 the i^(th) operation of the static table isnot included in the power change flow (e.g., as specified in a column ofthe static table) the method returns to block 1920 where i isincremented. If the i^(th) operation is included in the power changeflow, but at decision diamond 1926 the override entry indicates that thei^(th) operation is not to be executed (e.g., a modification of the flowhas been implemented), returning to block 1920 the index i isincremented and the i^(th) operation in the static table is to beconsidered at decision diamond 1924.

FIG. 20 is a flow diagram of a method, according to another embodimentof the present invention. Method 2000 begins at block 2010, where apower management agent (PMA) of a core of a processor receives from,e.g., a power management unit (PMU) of the processor, an indication tochange power consumption of the core. Continuing to decision diamond2012, if there are no override values to be received from the PMU,advancing to block 2016 a power change flow, e.g., a subset ofoperations (e.g., identified by a corresponding flow column) stored in astatic table, is executed by the PMA, and the method ends at 2050. Ifthe PMU has override values to be stored in the PMA, advancing fromdecision diamond 2012 to block 2014, the PMA stores the override valuesinto storage locations of an override column in a control register ofthe PMA. Proceeding to block 2030, operations indicated by contents ofthe override column are to be executed. That is, the override columndictates execution of a modified flow to be executed instead of thepower change flow stored in a static table. The method ends at 2050.

Additional embodiments are described below.

In a first embodiment, a processor includes at least one core includinga first core, and a power management agent (PMA) coupled to the firstcore. The PMA may include a static table to store a list of operations,and that includes a plurality of columns, each column to specify acorresponding flow, each flow to include a corresponding subset of theoperations and each flow associated with a corresponding state of thefirst core; a control register (CR) to include a plurality of storageelements, wherein each storage element corresponds to a respectiveoperation listed in the static table, each storage element to receiveone of a first value and a second value; and execution logic, responsiveto a command to place the first core into a first state, to execute eachoperation of a first flow for which the corresponding storage elementstores the first value and to refrain from execution of each operationof the first flow for which the corresponding element stores the secondvalue.

A 2^(nd) embodiment includes elements of the 1^(st) embodiment, whereupon execution of the first subset in accordance with contents of thestorage elements, the core is to transition from a sleep state to anactive state.

A 3^(rd) embodiment includes elements of the 1^(st) embodiment, whereupon execution of the first subset in accordance with contents of thestorage elements, the first core is to be placed into a sleep state.

A 4^(th) embodiment includes elements of the 1^(st) embodiment, whereupon execution of the first subset in accordance with contents of thestorage elements, the first core is to be in a reduced activity state.

A 5^(th) embodiment includes elements of the 1^(st) embodiment, where ina first pass the execution logic is to execute the first subset inaccordance with first contents of the storage elements, and in a secondpass to execute the first subset according to second contents of thestorage elements, and wherein execution of the first pass and the secondpass is equivalent to a switch in sequence of two successive operationsof the first subset.

A 6^(th) embodiment includes elements of any one of embodiments 1 to 5,and further includes a power management unit (PMU) to determine acorresponding value to be stored in each of the storage elements of theCR.

A 7^(th) embodiment includes elements of any one of embodiments 1 to 5,where a corresponding value to be stored in each of the elements of theCR is to be determined based on user input.

An 8^(th) embodiment includes a processor that includes at least onecore including a first core, and a power management agent (PMA)including: a table to statically store a list of operations, the tableto include a first column to specify a first subset of the list ofoperations, wherein upon execution of the first subset operation of thefirst core is changed from a first state to a second state; a controlregister (CR) that includes a plurality of storage elements todynamically store contents, each storage element associated with acorresponding operation listed in the static table, where the CR is tospecify a second subset of the list of operations; and execution logicto execute operations, where responsive to a command to place the firstcore into the first state, the execution logic is execute the secondsubset specified by contents of the CR instead of execution of the firstsubset specified by contents of the first column of the table and as aresult of execution of the second set operation of the first core is tobe changed from the first state to the second state.

A 9^(th) embodiment includes elements of the 8^(th) embodiment, wherethe first state is a powered down state and the second state is apowered up state.

A 10^(th) embodiment includes elements of the 8^(th) embodiment, whereinthe first state is a powered up state and the second state is a powereddown state.

An 11^(th) embodiment includes elements of the 8^(th) embodiment, wherethe first state is a powered up state and the second state is apartially powered down state.

A 12^(th) embodiment includes elements of the 8^(th) embodiment, wherethe execution logic is to execute the second subset of the operation setin a first pass according to first contents of the CR, and subsequentlyto execute a third subset of the operation set in a second passaccording to second contents of the CR, where the first contents of theCR differs from the second contents of the CR.

A 13^(th) embodiment includes elements of the 12^(th) embodiment, whereexecution of the second subset followed by execution of the third subsetproduces a reversal of a sequence of two successive operations of thelist of operations.

A 14^(th) embodiment includes elements of the 12^(th) embodiment, whereexecution of the second subset followed by execution of the third subsetis to result in execution of single operation, and when execution of thesingle operation is complete execution is halted.

A 15^(th) embodiment includes elements of any one of embodiments 8 to14, and further includes a power management unit (PMU) to determine acorresponding value to be stored in each of the storage elements of theCR.

A 16^(th) embodiment is a machine-readable medium having stored thereondata, which if used by at least one machine, causes the at least onemachine to fabricate at least one integrated circuit to perform a methodthat includes: receiving a command to execute a first flow to change anoperating parameter of a core of a processor, where the first flow isspecified by a sequence stored in a static storage, the sequence toindicate an execution order of a first portion of a plurality ofoperations; storing, into dynamic storage elements of a control register(CR), a modified sequence that specifies the execution order of a secondportion of the plurality of operations; and responsive to the command,executing the modified sequence according to contents of the controlregister instead of executing the first flow according to contents ofthe static storage.

A 17^(th) embodiment includes elements of the 16^(th) embodiment, whereupon execution of the modified sequence the core is to go into a reducedpower state.

An 18^(th) embodiment includes elements of the 16^(th) embodiment, whereupon execution of the modified sequence the core is to go into a poweredup state.

A 19^(th) embodiment includes elements of the 16^(th) embodiment, andfurther includes receiving the contents of the CR from a powermanagement unit (PMU) of the processor.

A 20^(th) embodiment includes elements of the 16^(th) embodiment, whereexecution of the modified sequence is to result in a reset of the coreafter a shutdown.

A 21^(st) embodiment is a method that includes: receiving a command toexecute a first flow to change an operating parameter of a core of aprocessor, wherein the first flow is specified by a sequence stored in astatic storage, the sequence to indicate an execution order of a firstportion of a plurality of operations; storing, into dynamic storageelements of a control register (CR), a modified sequence that specifiesthe execution order of a second portion of the plurality of operations;and responsive to the command, executing the modified sequence accordingto contents of the control register instead of executing the first flowaccording to contents of the static storage.

A 22^(nd) embodiment includes elements of the 21^(st) embodiment, whereupon execution of the modified sequence the core is to go into a reducedpower state.

A 23^(rd) embodiment includes elements of the 21^(st) embodiment, whereupon execution of the modified sequence the core is to go into a poweredup state.

A 24^(th) The embodiment includes elements of the 21^(st) embodiment,and further includes receiving the contents of the CR from a powermanagement unit (PMU) of the processor.

A 25^(th) embodiment includes elements of the 21^(st) embodiment, whereexecution of the modified sequence is to result in a reset of the coreafter a core shutdown.

A 26^(th) embodiment is an apparatus to perform the method of any one ofembodiments 21-25.

A 27^(th) embodiment includes apparatus comprising means for performingthe method of any one of embodiments 21-25.

A 28^(th) embodiment includes system that includes at least one coreincluding a first core, and a dynamic random access memory (DRAM) thatincludes storage and a power management agent (PMA) coupled to thestorage, the PMA to include: a static table to store a list ofoperations, and that includes a plurality of columns, each column tospecify a corresponding flow, each flow to include a correspondingsubset of the operations and each flow associated with a correspondingstate of the storage; a control register (CR) to include a plurality ofstorage elements, where each storage element corresponds to a respectiveoperation listed in the static table, each storage element to receiveone of a first value and a second value; and execution logic, responsiveto a command to place the DRAM into a first state, to execute eachoperation of a first flow for which the corresponding storage elementstores the first value and to refrain from execution of each operationof the first flow for which the corresponding element stores the secondvalue.

A 29^(th) embodiment includes elements of the 28^(th) embodiment, whereupon execution of the first flow in accordance with contents of thestorage elements, the DRAM is to go into a reset state.

A 30^(th) embodiment includes elements of the 28^(th) embodiment, whereupon execution of the first flow in accordance with contents of thestorage elements the DRAM is to go into a reduced power state.

Embodiments may be used in many different types of systems. For example,in one embodiment a communication device can be arranged to perform thevarious methods and techniques described herein. Of course, the scope ofthe present invention is not limited to a communication device, andinstead other embodiments can be directed to other types of apparatusfor processing instructions, or one or more machine readable mediaincluding instructions that in response to being executed on a computingdevice, cause the device to carry out one or more of the methods andtechniques described herein.

Embodiments may be implemented in code and may be stored on anon-transitory storage medium having stored thereon instructions whichcan be used to program a system to perform the instructions. Embodimentsalso may be implemented in data and may be stored on a non-transitorystorage medium, which if used by at least one machine, causes the atleast one machine to fabricate at least one integrated circuit toperform one or more operations. The storage medium may include, but isnot limited to, any type of disk including floppy disks, optical disks,solid state drives (SSDs), compact disk read-only memories (CD-ROMs),compact disk rewritables (CD-RWs), and magneto-optical disks,semiconductor devices such as read-only memories (ROMs), random accessmemories (RAMs) such as dynamic random access memories (DRAMs), staticrandom access memories (SRAMs), erasable programmable read-only memories(EPROMs), flash memories, electrically erasable programmable read-onlymemories (EEPROMs), magnetic or optical cards, or any other type ofmedia suitable for storing electronic instructions.

While the present invention has been described with respect to a limitednumber of embodiments, those skilled in the art will appreciate numerousmodifications and variations therefrom. It is intended that the appendedclaims cover all such modifications and variations as fall within thetrue spirit and scope of this present invention.

What is claimed is:
 1. A processor comprising: at least one coreincluding a first core; and a power management agent (PMA) coupled tothe first core, the PMA to include: a static table to store a list ofoperations, and that includes a plurality of columns, each column tospecify a corresponding flow, each flow to include a correspondingsubset of the operations and each flow associated with a correspondingstate of the first core; a control register (CR) to include a pluralityof storage elements, wherein each storage element corresponds to arespective operation listed in the static table, each storage element toreceive one of a first value and a second value; and execution logic,responsive to a command to place the first core into a first state, toexecute each operation of a first flow for which the correspondingstorage element stores the first value and to refrain from execution ofeach operation of the first flow for which the corresponding elementstores the second value.
 2. The processor of claim 1, further includinga power management unit (PMU) to determine a corresponding value to bestored in each of the storage elements of the CR.
 3. The processor ofclaim 1, wherein upon execution of the first subset in accordance withcontents of the storage elements, the core is to transition from a sleepstate to an active state.
 4. The processor of claim 1, wherein uponexecution of the first subset in accordance with contents of the storageelements, the first core is to be placed into a sleep state.
 5. Theprocessor of claim 1, wherein upon execution of the first subset inaccordance with contents of the storage elements, the first core is tobe in a reduced activity state.
 6. The processor of claim 1, wherein ina first pass the execution logic is to execute the first subset inaccordance with first contents of the storage elements, and in a secondpass to execute the first subset according to second contents of thestorage elements, and wherein execution of the first pass and the secondpass is equivalent to a switch in sequence of two successive operationsof the first subset.
 7. The processor of claim 1, wherein acorresponding value to be stored in each of the elements of the CR is tobe determined based on user input.
 8. A machine-readable medium havingstored thereon data, which if used by at least one machine, causes theat least one machine to fabricate at least one integrated circuit toperform a method comprising: receiving a command to execute a first flowto change an operating parameter of a core of a processor, wherein thefirst flow is specified by a sequence stored in a static storage, thesequence to indicate an execution order of a first portion of aplurality of operations; storing, into dynamic storage elements of acontrol register (CR), a modified sequence that specifies the executionorder of a second portion of the plurality of operations; and responsiveto the command, executing the modified sequence according to contents ofthe control register instead of executing the first flow according tocontents of the static storage.
 9. The machine-readable medium of claim8, wherein upon execution of the modified sequence the core is to gointo a reduced power state.
 10. The machine-readable medium of claim 8,wherein upon execution of the modified sequence the core is to go into apowered up state.
 11. The machine-readable medium of claim 10, furthercomprising receiving the contents of the CR from a power management unit(PMU) of the processor.
 12. The machine-readable medium of claim 8,wherein execution of the modified sequence is to result in a reset ofthe core after a shutdown.
 13. A processor comprising: a first corehaving a power management agent (PMA), the PMA comprising: a table tostatically store a list of operations including a first subset of thelist of operations, wherein upon execution of the first subset,operation of the first core is to be changed from a first state to asecond state; a control register (CR) having a plurality of storageelements, each storage element associated with a corresponding operationstored in the table, wherein the CR is to specify a second subset of thelist of operations; and execution logic to execute operations, whereinresponsive to a command to place the first core into the first state,the execution logic is to execute the second subset specified by the CRand not the first subset stored in the table, wherein the execution ofthe second subset is to change operation of the first core from thefirst state to the second state; and a power management unit (PMU) todetermine a corresponding value to be stored in each of the storageelements of the CR.
 14. The processor of claim 13, wherein the firststate is a powered down state and the second state is a powered upstate.
 15. The processor of claim 13, wherein the first state is apowered up state and the second state is a partially powered down state.16. The processor of claim 13, wherein the execution logic is to executethe second subset in a first pass according to first contents of the CR,and subsequently to execute a third subset of the list of operations ina second pass according to second contents of the CR, wherein the firstcontents of the CR differ from the second contents of the CR.
 17. Theprocessor of claim 16, wherein the processor is to execute the secondsubset followed by the third subset to produce a reversal of a sequenceof two successive operations of the list of operations.
 18. Theprocessor of claim 17, wherein the processor is to execute the secondsubset followed by the third subset to execute a single operation, andthereafter halt execution.